The present invention relates generally to steered beam antenna arrays. More specifically, but without limitation thereto, the present invention relates to a method for selecting amplitudes and phases of a drive signal input to elements of a multiple element antenna to approximate a radiation pattern having a desired beamwidth, sidelobe level and gain.
Multiple element antennas, or antenna arrays, are used in many commercial and military systems. An example of such an antenna array used on surface ships is a circular array of 64 dipoles, where each dipole is inside a cavity. The power distribution and phase shift of the transmit signal input to each antenna element is typically controlled by phase shifters, switches, and a waveguide. The parameters of beamwidth, sidelobe level and gain are currently improved by increasing the size of the array. The larger array size has the disadvantage of consuming valuable space on the uppermost areas of the ship. Previous methods for optimizing performance of an antenna array calculate the amplitude and phase drive current at each antenna element to generate a desired beam pattern. These methods typically place the largest amplitudes in the center of the array and the smallest amplitudes at the ends of the array. A disadvantage of these methods is that a large array diameter is required to achieve stringent beamwidth, sidelobe level, and gain parameters.
A need therefore continues to exist for a method for meeting goals of beamwidth, sidelobe level, and gain parameters of an antenna array while decreasing the size of the array.